Detector-amplifier circuit arrangement



April 16, 1940. H. PITSCH 2,197,346

DETECTOR-AMPLIFIER CIRCUIT ARRANGEMENT Filed March 17, 1938 0 v L s INVENTOR H; P/TSCH ATTORNEY Patented Apr. 15, 1940 DETECTOR-AMPLIFIER CIRCUIT ARRANGE MINT Helmut Pitsch, Berlin, Germany, assignor to Tele-- funken Gesellschaft fiir Drahtlose Telegraphic, m. b. H., Berlin,: Germany,,a corporation of Germany 1 Application March 17,

3 Claims.

The general aim in the use and operation of receivers is to resort to diode rectification and to impress the diode with as high an RF potential as possible to the end of insuring demodula tion free from distortion.

In order to obtain a high RF potential, of course, high RF gain must be provided, and the incidental cost may in part be recovered by a reduction of the number of tubes of the AF amplifier. However, this plan involves the-drawback that the AF amplification will not always suflice for phonograph operation. It is known in the art that this drawback may be avoided by using an RF amplifier tube for AF amplification after the apparatus has been changed to phonograph record reproduction. This, in turn, makes it diflicult to outbalance or decouple the various stages.

It is also known in the prior art that aone- 20 grid tube or diode may, at will, be used to act as a diode rectifier for reception and as an amplifier for phonograph disk record reproduction.

However, in this circuit organization known in the art, three switches were required,'and this 25 leaves the impression as if such change-over is very complicated.

However, as proved by the present invention,

it is possible to get along with a single switch or that, at most, two switches are required, if not only the connections of the tube are to be changed, but if in addition withdrawal of the sound pickup from the sockets is to be avoided and a circuit element serving for coupling with the next tube or stage. In other words, the basic idea of the invention will be found useful also in a case where recourse is to be had at will either to an amplifying detection or to straight diode rectification.

A few exemplified embodiments of the invention shall be hereinafter explained in more detail by reference to the drawing, wherein Fig. 1 discloses a circuit arrangement embodying the invention, and Figs. la, 2, 2a, 3 and 3a show various modifications.

Referring to Fig. 1, the two positions of the switch S for diode rectification and amplifying detection are designated by D and V, respective- In Germany April 3, 1937 193's, Serial mgisaszs ly. In the left-hand position, at D, anode and grid of tube R are interconnected. In the other position, V, the anode which is always united With the coupling condenser C, is connected also with the plate resistance W. TA designates the sockets for plugging in the pick-up. For instance, when the pick-up is to be disconnected with the waveband switch, then the grid of tube R is connected at will with the condenser K or the upper terminal of TA. For phonograph record reproduction a negative biasing voltage G will in this case be automatically rendered operative.

As shown in Fig. la, the invention is useful also when the load resistanceB is connected in series relation rather than in parallel relation with the oscillation circuit.

In these two circuit organizations as well as in those following recourse could be had to feedback, for instance, as indicated by the dash-lines in Fig. 3. Inasmuch as the same is active in the circuit schemes Figs. 1 and 10, only in the amplifying position, it serves a purpose only when the invention is applied not to phonograph record reproduction, but to the change-over from diode rectification to grid-current or plate-current rectification.

In the schemes shown in Figs. 2 and 2a,the switch arm Sis not connected with the anode, but to the coupling means provided to establish coupling relation with the next tube or stage, the said coupling means consisting of resistance-capacity coupling or of a transformer (shown above the former). In this connection is required a condenser C1 in order that in the diode-rectification position the plate potential may be precluded from the grid. Also in this instance, feedback has sense only when grid-detection is to be used for reception.

Figs. 3 and 3a. show another scheme in which the switch lever, as in Figs. 2 and 2a, is connected with the coupling condenser C; but the plate resistance W is associated with the switch terminal V according to Figs. 1 and 1a rather than with the coupling condenser. In both circuit organizations Figs. 3 and 3a, feedback, if provided, is operative unless the sound pickup is connected.

What I claim is: I

1. A receiving circuit including a vacuum tube having a cathode, a signal control grid and an anode, an input circuit connected between the cathode and grid, a load resistor included in said circuit, a pair of contacts one being connected to I the control grid and the other being connected through a resistor to the positive side of a source of potential, and a switch member permanently connected to the anode and adapted selectively to contactv the first mentioned contact to enable the tube to operate as a diode detector and to contact the second mentioned contact to enable the tube to operate as an audio amplifier.

2. A receiving circuit including a vacuum tube having a cathode, a signal control grid and an anode, a resonant circuit connected between the cathode and grid, a load resistor connected in shunt to said resonant circuit, a pair of contacts one being connected to the grid side of the load resistor and the other being connected through a resistor to the positive side of a source of potential, and a switch member permanently connected to the anode and adapted selectively to contact the first mentioned contact to enable the tube to operate as a diode detector and to contact the second mentioned contact to enable the tube to operate as an audio amplifier.

3. A receiving circuit including a vacuum tube having a cathode, a signal control grid and an anode, a resonant circuit connected between the cathode and grid, a load resistor serially connected between cathode and said resonant circuit, a pair of contacts one being connected to the grid side of the load resistor and the other being connected through a resistor to the positive side of a source of potential, and a switch member permanently connected to the anode and adapted selectively to contact the first mentioned contact to enable the tube to operate as a diode detector and to contact the second mentioned contact to enable the tube to operate as an audio. amplifier.

HELMUT PITSCH. 

